
<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title>canvas clock</title>
		<style type="text/css">
			div{
				text-align: center;
				margin-top: 250px;
			}
			#clock{
				border: 1px solid #ccc;
			}
		</style>
	</head>
	<body>
		<div>
			<canvas id="clock" height="200px" width="200px"></canvas>
		</div>
		<script type="text/javascript" src="clock.js"></script>
		
	</body>
 
</html>
 
<script>
var dom=document.getElementById('clock');
var ctx=dom.getContext('2d');
var width=ctx.canvas.width;
var height=ctx.canvas.height;
var r=width/2;
function drawBackground(){
	ctx.save();
	ctx.translate(r,r)
	ctx.beginPath();
	ctx.lineWidth=10;
	ctx.arc(0,0,r-5,0,2*Math.PI,false);
	ctx.stroke();
	var hourNumbers=[3,4,5,6,7,8,9,10,11,12,1,2];
	ctx.font='18px Arial';
	ctx.textAlign='center';
	ctx.textBaseline='middle';
	hourNumbers.forEach(function(number,i){
		var rad=2*Math.PI/12*i;
		var x=Math.cos(rad)*(r-30);
		var y=Math.sin(rad)*(r-30);
		ctx.fillText(number,x,y);
		
	});
	for(var i=0;i<60;i++){
		var rad=2*Math.PI/60*i;
		var x=Math.cos(rad)*(r-18);
		var y=Math.sin(rad)*(r-18);
		ctx.beginPath();
		if(i%5==0){
			ctx.fillStyle='#000';
			ctx.arc(x,y,2,0,2*Math.PI,false);
		}else{
			ctx.fillStyle='#ccc';
			ctx.arc(x,y,2,0,2*Math.PI,false);
		}
		ctx.fill();
	}
}
	function drawHour(hour,minute){
		ctx.save();
		ctx.beginPath();
		var rad=2*Math.PI/12*hour;
		var mrad=2*Math.PI/12/60*minute;
		ctx.rotate(rad+mrad);
		ctx.lineWidth=6;
		ctx.lineCap='round';
		ctx.moveTo(0,10);
		ctx.lineTo(0,-r/2);
		ctx.stroke();
		ctx.restore();
	}
	function drawMinute(minute){
		ctx.save();
		ctx.beginPath();
		var rad=2*Math.PI/60*minute;
		ctx.rotate(rad);
		ctx.lineWidth=3;
		ctx.lineCap='round';
		ctx.moveTo(0,10);
		ctx.lineTo(0,-r+30);
		ctx.stroke();
		ctx.restore();
	}
	function drawSecond(second){
		ctx.save();
		ctx.beginPath();
		ctx.fillStyle='#c14543';
		var rad=2*Math.PI/60*second;
		ctx.rotate(rad);
		ctx.moveTo(-2,20);
		ctx.lineTo(2,20);
		ctx.lineTo(1,-r+18);
		ctx.lineTo(-1,-r+18);
		ctx.fill();
		ctx.restore();
	}
	function drawDot(){
		ctx.beginPath();
		ctx.fillStyle="#fff";
		ctx.arc(0,0,3,0,2*Math.PI,false);
		ctx.fill();
	}
 function draw(){
 ctx.clearRect(0,0,width,height);
var now =new Date();
var hour=now.getHours();
var minute=now.getMinutes();
var second=now.getSeconds();
drawBackground();
drawHour(hour,minute);
drawMinute(minute);
drawSecond(second);
drawDot();
ctx.restore();
 }
 draw();
 setInterval(draw,1000);//每秒执行代码
</script>